This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The long-term goal of this project is to examine the possible effects of atrazine and its metabolites on aquatic macroinvertebrates found in streams and rivers in North Dakota. Atrazine is a commonly used herbicide that persists in aquatic systems and has recently been shown to act as an endocrine disrupter in a variety of organisms. There is currently little research being done in North Dakota on atrazine in aquatic systems. In addition, there is a need for more data on the effects of this herbicide on aquatic organisms. The popular approach to toxicity testing is to perform single species tests in a controlled microcosm and then extrapolate the results to natural occurring environments. Often the species examined are those that have been easily cultured in past testing and may not have any relationship to the species occurring in local aquatic ecosystems. This approach has been criticized because of its artificiality. We will take a different approach, we will use field collected data to determine which species should be considered for toxicity testing. Local species and conditions will be considered in all phases of our investigations.[unreadable] This study will investigate several areas of concern regarding atrazine in aquatic systems. It will address the prevalence of atrazine in aquatic systems, examine this prevalence with the known macroinvertebrate fauna, identify aquatic macroinvertebrate fauna that may be indicative of atrazine contamination, and examine what effects atrazine may have on aquatic macroinvertebrates. Because of atrazine's action as an endocrine disrupter in mammalian systems, there is considerable concern with the possible implications exposure may have on human systems. Atrazine is widespread and a common component of surface waters in agricultural areas. Current water testing procedures require extensive chemical analysis. The discovery of a bioindicator for atrazine contamination would be beneficial in documenting possible exposure routes for atrazine to humans. [unreadable][unreadable][unreadable][unreadable]